The present invention relates to a power brake booster for an automotive vehicle, with a housing subdivided into two compartments by a partition wall, the said compartments comprising each in a booster close to the brake pedal and in a booster close to the master cylinder one vacuum chamber of constant pressure and one working chamber of variable pressure, wherein a control housing slidable in the actuating direction accommodates a valve device which cooperates with the piston rod of the brake pedal and governs the introduction of atmospheric air into the working chambers, a push rod being operatively connected with the control housing and displacing the piston of the master cylinder.
In a known power brake booster (FR-PS No. 1,537,497), the connection of the two vacuum chambers is effected such that the housing of the power brake booster is of larger diameter on the master cylinder side than it is on the brake pedal side. Inserted into the portion of larger diameter is a cylindrical bowl whose bottom constitutes the partition wall of the power brake booster. An annular chamber is formed between the inserted cylindrical bowl and the larger-diameter housing portion of the power brake booster through which chamber the vacuum is allowed to propagate from one vacuum chamber to the other.
It is the disadvantage of the priorly known power brake booster that it is of relatively complicated design. It is above all disadvantageous in respect of costs that the cylindrical bowl has to be held by spacer elements within the housing of the power brake booster. Mounting of such a cylindrical bowl necessitates considerable effort that makes the power brake booster more expensive. The outer diameter of the power brake booster is increased as well as the number of components.
Further, a power brake booster of the type at issue is known (German printed and published patent application No. 29 18 915), wherein the booster piston close to the master cylinder is sealingly connected with the partition wall by a rolling diaphragm, wherein channels extend in a longitudinal direction between the housing and the rolling diaphragm to interconnect the two vacuum chambers, and wherein the rolling diaphragm is equipped with axially extending webs on its side rolling off on the outer wall of the housing.
Likewise this priorly known power brake booster bears the disadvantage of being comparatively expensive in its manufacture, in particular the assembly of the diaphragm furnished with several webs entails intricate work.
It is an object of the present invention to arrange for a power brake booster for an automotive vehicle which avoids the shortcomings of the prior art and which, in addition, enables a maximum possible effective diameter of the booster pistons, their outer diameter being predetermined. Finally, the inventive power brake booster is employs a type of construction which saves as much weight as possible, in particular owing to the housing shells' design.